Distance measurement device, distance measurement method, and distance measurement program

ABSTRACT

A distance measurement device includes an imaging unit which captures a subject image formed by an imaging optical system, an emission unit which emits directional light as light having directivity along an optical axis direction of the imaging optical system, a light receiving unit which receives reflected light of the directional light from the subject, a derivation unit which derives a distance to the subject based on the timing at which the directional light is emitted and the timing at which the reflected light is received, a display unit which displays the subject image, and a control unit which performs control such that, in a case of performing a distance measurement, the display unit displays the subject image as a motion image and transition is made to a state where actual exposure by the imaging unit is possible at the timing of the end of the distance measurement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.16/687,895, filed on Nov. 19, 2019, which is a continuation applicationof application Ser. No. 15/413,416, filed on Jan. 24, 2017, which acontinuation application of International Application No.PCT/JP2015/061741, filed on Apr. 16, 2015, the entire contents of theseapplications are incorporated herein by reference in their entirety.Further, this application claims priority from Japanese PatentApplication No. 2014-159735, filed on Aug. 5, 2014, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND Technical Field

A technique of the present disclosure relates to a distance measurementdevice, a distance measurement method, and a distance measurementprogram.

Description of the Related Art

JP2008-96181A discloses a device including time detection means fordetecting the time from the emission of measurement light to thereception of measurement light by light receiving means, shake amountdetection means for detecting a shake amount of a housing duringemission of measurement light when measurement light is emitted fromlight emitting means, and distance determination means for determiningthe distance to an object to be measured based on the time detected bythe time detection means and the shake amount detected by the shakeamount detection means.

JP2002-207163A discloses a distance measurement and imaging devicehaving a function of performing focus adjustment, a distance measurementfunction of measuring a distance to a subject by irradiating the subjectwith a laser beam along an optical axis of a lens and detectingreflected light of the laser beam, and an imaging function of imagingthe subject.

However, in the technique of JP2008-96181A, the distance to the objectto be measured can be measured, but imaging of the object to be measuredis not considered.

In the technique of JP2002-207163A, since still image capture is notconsidered, if transition is made to still image capture during distancemeasurement, a live view image of the subject cannot be temporarilydisplayed, and the subject under a distance measurement cannot beconfirmed even though a distance measurement is being performed.

SUMMARY

The invention has been accomplished in consideration of theabove-described facts, and provides a distance measurement device, adistance measurement method, and a distance measurement program storagemedium capable of performing a distance measurement while confirming asubject even if still image capture is instructed.

A distance measurement device according to a first aspect of theinvention comprises an imaging unit which captures a subject imageformed by an imaging optical system forming the subject image indicatinga subject, an emission unit which emits directional light as lighthaving directivity along an optical axis direction of the imagingoptical system, a light receiving unit which receives reflected light ofthe directional light from the subject, a derivation unit which derivesa distance to the subject based on the timing at which the directionallight is emitted by the emission unit and the timing at which thereflected light is received by the light receiving unit, a display unitwhich displays the subject image captured by the imaging unit, and acontrol unit which performs control such that, in a case of performing adistance measurement by the emission unit, the light receiving unit, andthe derivation unit, the display unit displays the subject imagecaptured by the imaging unit as a motion image and transition is made toa state where actual exposure by the imaging unit is possible at thetiming of the end of the distance measurement. With this, the distancemeasurement device according to the first aspect of the invention canperform the distance measurement while confirming the subject even ifstill image capture is performed.

According to a second aspect of the invention, in the distancemeasurement device according to the first aspect of the invention, thetiming of the end of the distance measurement may be the timing of theend of a period during which light emission and light reception areperformed by the emission unit and the light receiving unit. With this,the distance measurement device according to the second aspect of theinvention can transition to the actual exposure without waiting untilthe distance is completely derived.

According to a third aspect of the invention, in the distancemeasurement device according to the first aspect of the invention, thetiming of the end of the distance measurement may be the timing of theend of a derivation period during which the distance is derived by thederivation unit. With this, the distance measurement device according tothe third aspect of the invention can reliably perform the distancemeasurement while confirming the subject since the subject image isdisplayed until the derivation of the distance is finished.

According to a fourth aspect of the invention, in the distancemeasurement device according to any one of the first to third aspects ofthe invention, the imaging unit may perform the actual exposure by theimaging unit in a case where the distance is derived by the derivationunit. With this, the distance measurement device according to the fourthaspect of the invention can reliably make the derived distancecorrespond to a captured image obtained by the actual exposure.

According to a fifth aspect of the invention, the distance measurementdevice according to any one of the first to fourth aspects of theinvention may further comprise a setting unit which sets the possibilityof the actual exposure by the imaging unit in advance in a case wherethe derivation of the distance by the derivation unit is impossible.With this, the distance measurement device according to the fifth aspectof the invention can arbitrarily set whether or not to perform theactual exposure in a case where the derivation of the distance isimpossible.

According to a sixth aspect of the invention, the distance measurementdevice according to any one of the first to fifth aspects of theinvention may further comprise a storage unit which stores the distancederived by the derivation unit, and in a case where the derivation ofthe distance by the derivation unit is impossible, storage by thestorage unit may be stopped. With this, the distance measurement deviceaccording to the sixth aspect of the invention can prevent storage ofincomplete distance data.

According to a seventh aspect of the invention, the distance measurementdevice according to the sixth aspect of the invention may furthercomprise a storage setting unit which sets whether or not to stopstorage by the storage unit in a case where the derivation of thedistance by the derivation unit is impossible. With this, the distancemeasurement device according to the seventh aspect of the invention canarbitrarily set whether or not to perform storage in the storage unit ina case where the derivation of the distance is impossible.

According to an eighth aspect of the invention, the distance measurementdevice according to any one of the first to seventh aspects of theinvention may further comprise a focus adjustment unit which performsfocus adjustment of the imaging optical system to the subject based onthe distance derived by the derivation unit. With this, the distancemeasurement device according to the eighth aspect of the invention caneasily perform focus adjustment at the time of the actual exposure.

According to a ninth aspect of the invention, in the distancemeasurement device according to any one of the first to eighth aspectsof the invention, the derivation unit may derive the distance in a casewhere there is no focus adjustment error by a focus adjustment unitperforming focus adjustment of the imaging optical system to the subjectand no exposure adjustment error by an exposure adjustment unitadjusting exposure in a case where the imaging unit performs imaging.With this, the distance measurement device according to the ninth aspectof the invention can display an image focused and subjected to focusadjustment until transition to a state where the actual exposure ispossible.

According to a tenth aspect of the invention, in the distancemeasurement device according to any one of the first to ninth aspects ofthe invention, the derivation unit may perform the derivation of thedistance multiple times, in a case of deriving a distance having a highfrequency among the distances obtained by deriving the distance multipletimes as a final distance, may determine a distance range for use indetermining the frequency and a time range from the emission to thereception of the directional light based on an adjustment result of afocus adjustment unit performing focus adjustment of the imaging opticalsystem to the subject, and may derive the distance to the subject with aresolution determined according to a determined result. With this, thedistance measurement device according to the tenth aspect of theinvention can derive the distance to the subject in units of minutenumerical values.

According to an eleventh aspect of the invention, in the distancemeasurement device according to any one of the first to tenth aspects ofthe invention, the emission unit may be able to adjust the emissionintensity of the directional light, and in a case of deriving thedistance, may adjust the emission intensity based on an adjustmentresult of a focus adjustment unit performing focus adjustment of theimaging optical system to the subject to emit the directional light.With this, the distance measurement device according to the eleventhaspect of the invention can derive the distance to the subject withproper emission intensity not affected by noise of ambient light.

According to a twelfth aspect of the invention, in the distancemeasurement device according to the eleventh aspect of the invention,the emission unit may make the emission intensity lower when a focaldistance adjusted by the focus adjustment unit is shorter. With this,the distance measurement device according to the twelfth aspect of theinvention can derive the distance to the subject with proper emissionintensity not affected by noise of ambient light.

According to a thirteenth aspect of the invention, in the distancemeasurement device according to any one of the first to twelfth aspectsof the invention, the light receiving unit may be able to adjust lightreceiving sensitivity, and in a case of deriving the distance, mayadjust the light receiving sensitivity based on an adjustment result ofa focus adjustment unit performing focus adjustment of the imagingoptical system to the subject to receive the reflected light. With this,the distance measurement device according to the thirteenth aspect ofthe invention can derive the distance to the subject with proper lightreceiving sensitivity not affected by noise of ambient light.

According to a fourteenth aspect of the invention, in the distancemeasurement device according to the thirteenth aspect of the invention,the light receiving unit may make the light receiving sensitivity lowerwhen a focal distance adjusted by the focus adjustment unit is shorter.With this, the distance measurement device according to the fourteenthaspect of the invention can derive the distance to the subject withproper light receiving sensitivity not affected by noise of ambientlight.

According to a fifteenth aspect of the invention, in the distancemeasurement device according to any one of the first to fourteenthaspects of the invention, the emission unit may be able to adjust theemission intensity of the directional light and may adjust the emissionintensity based on subject brightness or exposure state specificationinformation to emit the directional light. With this, the distancemeasurement device according to the fifteenth aspect of the inventioncan derive the distance to the subject with proper emission intensitynot affected by noise of ambient light.

According to a sixteenth aspect of the invention, in the distancemeasurement device according to the fifteenth aspect of the invention,the emission unit may make the emission intensity lower when the subjectbrightness is lower or exposure indicated by the exposure statespecification information is higher. With this, the distance measurementdevice according to the sixteenth aspect of the invention can derive thedistance to the subject with proper emission intensity not affected bynoise of ambient light.

According to a seventeenth aspect of the invention, in the distancemeasurement device according to any one of the first to sixteenthaspects of the invention, a distance measurement by the emission unit,the light receiving unit, and the derivation unit may be performed anumber of times determined in advance according to subject brightness orexposure state specification information. With this, the distancemeasurement device according to the seventeenth aspect of the inventioncan obtain a distance measurement result, in which the influence ofnoise of ambient light is moderated, compared to a case where the lightemission frequency of directional light is fixed regardless of subjectbrightness.

According to an eighteenth aspect of the invention, in the distancemeasurement device according to the seventeenth aspect of the invention,a distance measurement by the emission unit, the light receiving unit,and the derivation unit may be performed a larger number of times whenthe subject brightness is higher or when the exposure indicated by theexposure state specification information is lower. With this, thedistance measurement device according to the eighteenth aspect of theinvention can obtain a distance measurement result, in which theinfluence of noise of ambient light is moderated, compared to a casewhere the light emission frequency of directional light is fixedregardless of high subject brightness.

According to a nineteenth aspect of the invention, in the distancemeasurement device according to any one of the first to eighteenthaspect of the invention, in a case of performing the actual exposure bythe imaging unit, the emission of the directional light by the emissionunit and the light reception by the light receiving unit may be paused.With this, the distance measurement device according to the nineteenthaspect of the invention can prevent noise caused by directional lightfrom being superimposed on a captured image.

A distance measurement method according to a twentieth aspect of theinvention comprises causing an imaging unit to capture a subject imageformed by an imaging optical system forming the subject image indicatinga subject, displaying the captured subject image on a display unit as amotion image, emitting directional light as light having directivityalong an optical axis direction of the imaging optical system, receivingreflected light of the directional light from the subject, performing adistance measurement to derive a distance to the subject based on thetiming at which the directional light is emitted and the timing at whichthe reflected light is received, and performing control such thattransition is made to a state where actual exposure by the imaging unitis possible at the timing of the end of the distance measurement. Withthis, the distance measurement method according to the twentieth aspectof the invention can perform the distance measurement while confirmingthe subject even if still image capture is performed.

A distance measurement program according to a twenty-first aspect of theinvention causes a computer to execute processing including, in a caseof performing a distance measurement to derive a distance to a subjectbased on the timing at which directional light is emitted by an emissionunit emitting the directional light along an optical axis direction ofan imaging optical system forming a subject image indicating the subjectand the timing at which reflected light is received by a light receivingunit receiving the reflected light of the directional light from thesubject, displaying the subject image captured by an imaging unitcapturing the subject image on a display unit as a motion image andtransitioning to a state where actual exposure by the imaging unit ispossible at the timing of the end of the distance measurement. Withthis, the distance measurement program according to the twenty-firstaspect of the invention can perform the distance measurement whileconfirming the subject even if still image capture is performed.

According to a twenty-second aspect of the invention, there is provideda non-transitory computer-readable storage medium storing a distancemeasurement program, the distance measurement program causing a computerto execute distance measurement processing, and the distance measurementprocessing including causing an imaging unit to capture a subject imageformed by an imaging optical system forming the subject image indicatinga subject, displaying the captured subject image on a display unit as amotion image, emitting directional light as light having directivityalong an optical axis direction of the imaging optical system, receivingreflected light of the directional light from the subject, performing adistance measurement to derive a distance to the subject based on thetiming at which the directional light is emitted and the timing at whichthe reflected light is received, and performing control such thattransition is made to a state where actual exposure by the imaging unitis possible at the timing of the end of the distance measurement. Withthis, in the storage medium according to the twenty-second aspect of theinvention, it is possible to perform the distance measurement whileconfirming the subject even if still image capture is performed.

According to the technique of the present disclosure, it is possible toperform a distance measurement while confirming a subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of the configuration of amain part of a distance measurement device according to an embodiment.

FIG. 2 is a timing chart showing an example of the timing of a distancemeasurement operation to measure a distance to a subject in the distancemeasurement device according to the embodiment.

FIG. 3 is a timing chart showing an example of the timing from lightemission to light reception in a single measurement in the distancemeasurement device of the embodiment.

FIG. 4 is a graph showing an example of a histogram of measured valuesin a case where a distance to a subject is set as a horizontal axis anda measurement frequency is set as a vertical axis.

FIG. 5 is a flowchart showing an example of a flow of control processingwhich is executed by a main control unit in a case where a distancemeasurement imaging start button is provided in an operating unit in thedistance measurement device according to the embodiment.

FIG. 6 is a flowchart showing an example of a flow of distancemeasurement processing which is executed by a distance measurementcontrol unit in a case where the distance measurement imaging startbutton is provided in the operating unit in the distance measurementdevice according to the embodiment.

FIG. 7 is a flowchart showing an example of a flow of control processingwhich is executed by the main control unit in a case where a releasebutton is provided in the operating unit in the distance measurementdevice according to the embodiment.

FIG. 8 is a flowchart showing a modification example of the flow of thecontrol processing which is executed by the main control unit in a casewhere the distance measurement imaging start button is provided in theoperating unit in the distance measurement device according to theembodiment.

FIG. 9 is a flowchart showing a modification example of the flow of thedistance measurement processing which is executed by the distancemeasurement control unit in a case where the distance measurementimaging start button is provided in the operating unit in the distancemeasurement device according to the embodiment.

FIG. 10 is a flowchart showing a modification example of the flow of thecontrol processing which is executed by the main control unit in a casewhere the release button is provided in the operating unit in thedistance measurement device according to the embodiment.

FIG. 11A is a flowchart showing an example of distance measurement errorprocessing of the distance measurement control unit.

FIG. 11B is a flowchart showing an example of distance measurement errorprocessing of the main control unit in a case where a distancemeasurement error occurs before transition to still image capture(actual exposure) (when a distance measurement end signal is received).

FIG. 11C is a flowchart showing an example of distance measurement errorprocessing of the main control unit in a case where a distancemeasurement error occurs after still image capture (when distance datais received).

FIG. 12 is a conceptual diagram showing an example of the configurationof a light emission frequency determination table.

FIG. 13 is a flowchart showing an example of a flow of brightnessinformation transmission processing.

FIG. 14 is a flowchart showing an example of a flow of light emissionfrequency determination processing.

FIG. 15 is a conceptual diagram showing another example of theconfiguration of a light emission frequency determination table.

FIG. 16 is a flowchart showing another example of a flow of exposurestate specification information transmission processing.

FIG. 17 is a flowchart showing another example of a flow of lightemission frequency determination processing.

FIG. 18A is a graph showing a modification example of a histogramobtained in the distance measurement device according to the embodiment.

FIG. 18B is a graph showing a modification example of a histogramobtained in the distance measurement device according to the embodiment.

FIG. 18C is a graph showing a modification example of a histogramobtained in the distance measurement device according to the embodiment.

FIG. 19 is a block diagram showing an example of adjustment of a drivevoltage based on AF and AE results.

DETAILED DESCRIPTION

Hereinafter, an example of an embodiment of a distance measurementdevice of the present disclosure will be described referring to theaccompanying drawings. In this embodiment, a measurement of a distanceto a subject to be a measurement target is referred to as a “distancemeasurement”.

First, the configuration of the distance measurement device according tothis embodiment will be described. FIG. 1 is a block diagram showing theconfiguration of a main part of a distance measurement device 10according to this embodiment.

The distance measurement device 10 of this embodiment has a function ofperforming a distance measurement and a function of imaging a subject togenerate a captured image indicating the subject. The distancemeasurement device 10 of this embodiment comprises a control unit 20, alight emitting lens 30, a laser diode 32, a light receiving lens 34, aphotodiode 36, an imaging optical system 40, an imaging element 42, anoperating unit 44, a view finder 46, and a storage unit 48.

The control unit 20 comprises a time counter 22, a distance measurementcontrol unit 24, and a main control unit 26. The time counter 22 has afunction of generating a count signal in each given period determined inadvance according to a signal (for example, a clock pulse) input fromthe main control unit 26 through the distance measurement control unit24.

The distance measurement control unit 24 has a function of performing adistance measurement under the control of the main control unit 26. Thedistance measurement control unit 24 of this embodiment controls thedriving of the laser diode 32 at the timing according to the countsignal generated by the time counter 22 to perform the distancemeasurement. The distance measurement control unit 24 functions as aderivation unit. Specific examples of the distance measurement controlunit 24 include an application specific integrated circuit (ASIC), afield-programmable gate array (FPGA), and the like. The distancemeasurement control unit 24 of this embodiment has a storage unit (notshown). Specific examples of the storage unit in the distancemeasurement control unit 24 include a nonvolatile storage unit, such asa read only memory (ROM), and a volatile storage unit, such as a randomaccess memory (RAM).

The main control unit 26 has a function of controlling the entiredistance measurement device 10. The main control unit 26 of thisembodiment has a function of controlling the imaging optical system 40and the imaging element 42 to image a subject and generating a capturedimage (subject image). The main control unit 26 functions as a controlunit and a brightness detection unit. Specific examples of the maincontrol unit 26 include a central processing unit (CPU) and the like.The main control unit 26 of this embodiment has a storage unit (notshown). Specific examples of the storage unit in the main control unit26 include a nonvolatile storage unit, such as a ROM, and a volatilestorage unit, such as a RAM. A program of control processing describedbelow is stored in the ROM in advance.

A program of control processing is not necessarily stored in the maincontrol unit 26 from the beginning. For example, a control program maybe stored in advance in an arbitrary portable storage medium, such as asolid state drive (SSD), a CD-ROM, a DVD disk, a magneto-optical disk,or an IC card. The distance measurement device 10 may acquire thecontrol program from the portable storage medium storing the program andmay store the control program in the main control unit 26 or the like.Furthermore, the distance measurement device 10 may acquire the controlprogram from other external devices through the Internet or a local areanetwork (LAN) and may store the control program in the main control unit26 or the like.

The operating unit 44 is a user interface which is operated by the userwhen various instructions are provided to the distance measurementdevice 10. The operating unit 44 may include a distance measurementimaging start button for instructing the start time of a distancemeasurement and imaging, and buttons, keys, or the like (all of theseare not shown) for performing various instructions, or may include arelease button, and buttons, keys, or the like (all of these are notshown) for performing various instructions. Various instructionsreceived by the operating unit 44 are output to the main control unit 26as operation signals, and the main control unit 26 executes processingaccording to the operation signals input from the operating unit 44. Theoperating unit 44 may include a distance measurement instruction buttonfor instructing only a distance measurement, other than the above.

In a case where the distance measurement imaging start button isprovided in the operating unit 44, the distance measurement imagingstart button instructs the start of a distance measurement of thesubject and still image capture. In a case where the release button isprovided in the operating unit 44, the release button detects atwo-stage pressing operation of an imaging preparation instruction stateand an imaging instruction state. The imaging preparation instructionstate indicates, for example, a state of being pressed from a standbyposition to an intermediate position (half-pressing position), and theimaging instruction state indicates a state of being pressed to a finalpressing position (fully pressing position) beyond the intermediateposition. Hereinafter, “the state of being pressed from the standbyposition to the half-pressing position” refers to a “half-pressingstate”, and “the state of being pressed from the standby position or thehalf-pressing position to the fully pressing position” refers to a“fully pressing state”.

In the distance measurement device 10 according to this embodiment, amanual focus mode and an auto-focus mode are selectively set accordingto a user's instruction. In the auto-focus mode, in a case where thedistance measurement imaging start button is provided in the operatingunit 44, adjustment of imaging conditions is performed by operating thedistance measurement imaging start button to perform a distancemeasurement and imaging.

Specifically, the main control unit 26 controls the imaging opticalsystem 40 by operating the distance measurement imaging start button,whereby an automatic exposure (AE) function is operated to performexposure adjustment. After the exposure adjustment, an auto-focus (AF)function is operated to perform focus adjustment, subsequently, adistance measurement is performed, and then, imaging is performed. In acase where the release button is provided in the operating unit 44, theadjustment of the imaging conditions is performed by bringing therelease button into the half-pressing state to perform a distancemeasurement. Thereafter, exposure (imaging) is performed by successivelybringing the release button into the fully pressing state. That is, ifthe release button of the operating unit 44 is brought into thehalf-pressing state, the AE function is operated to perform exposureadjustment and a distance measurement, and the AF function is operatedto perform focus adjustment, and if the release button is brought intothe fully pressing state, imaging is performed.

The storage unit 48 primarily stores image data obtained by imaging, anda nonvolatile memory is used therefor. Specific examples of the storageunit 48 include a flash memory or a hard disk drive (HDD).

The view finder 46 has a function of displaying images, characterinformation, and the like. The view finder 46 of this embodiment is anelectronic view finder, and is used for displaying a live view image(through-image) as an example of a continuous-frame image obtained byimaging in continuous frames during imaging. The view finder 46 is alsoused for displaying a still image as an image of a single-frame imageobtained by imaging in a single frame in a case where an instruction tocapture a still image is provided. In addition, the view finder 46 isalso used for displaying a reproduced image in a reproduction image ordisplaying a menu screen or the like.

The imaging optical system 40 comprises an imaging lens including afocus lens, a motor, a slide mechanism, and a shutter (all of these arenot shown). The slide mechanism moves the focus lens along the opticalaxis direction (not shown) of the imaging optical system 40. The focuslens is attached so as to be slidable along the optical axis directionof the slide mechanism. The motor is connected to the slide mechanism,and the slide mechanism receives power of the motor and slides the focuslens along the optical axis direction. The motor is connected to themain control unit 26 of the control unit 20, and is controlled anddriven according to a command from the main control unit 26. In thedistance measurement device 10 of this embodiment, as a specific exampleof the motor, a stepping motor is applied. Accordingly, the motor isoperated in synchronization with pulse power in response to a commandfrom the main control unit 26.

In the distance measurement device 10 according to this embodiment, inthe auto-focus mode, the main control unit 26 performs focus adjustmentby driving and controlling the motor of the imaging optical system 40 ata position where a contrast value of an image obtained by imaging withthe imaging element 42 becomes the maximum. Furthermore, in theauto-focus mode, the main control unit 26 calculates AE informationwhich is a physical quantity indicating brightness of an image obtainedby imaging. The main control unit 26 derives a shutter speed and anF-number (aperture value) according to the brightness of the imageindicated by the AE information in a case where the release button ofthe operating unit 44 is brought into the half-pressing state. The maincontrol unit 26 performs exposure adjustment by controlling respectiverelated units in a state of becoming the derived shutter speed andF-number.

The imaging element 42 is an imaging element comprising color filters(not shown), and functions as an imaging unit. In this embodiment, as anexample of the imaging element 42, a CMOS type image sensor is used. Theimaging element 42 is not limited to a CMOS type image sensor, and mayby, for example, a CCD image sensor. The color filters include a Gfilter corresponding green (G) most contributing to obtaining abrightness signal, an R filter corresponding to red (R), and a B filtercorresponding to blue (B). Any filter of “R”, “G”, and “B” included inthe color filters is allocated to each of the pixels (not shown) of theimaging element 42.

In a case of imaging a subject, image light indicating the subject isformed on the light receiving surface of the imaging element 42 throughthe imaging optical system 40. The imaging element 42 has a plurality ofpixels (not shown) arranged in a matrix in a horizontal direction and avertical direction, and signal charges according to image light arestored in the pixels of the imaging element 42. The signal chargesstored in the pixels of the imaging element 42 are sequentially read asdigital signals according to the signal charges (voltages) under thecontrol of the main control unit 26.

The imaging element 42 has a so-called electronic shutter function, andoperates the electronic shutter function to control an electric chargestorage time (shutter sped) of each photosensor at the timing under thecontrol of the main control unit 26.

The imaging element 42 outputs the digital signals indicating the pixelvalues of the captured image from the respective pixels. The capturedimage output from the respective pixels is a chromatic image, and is,for example, a color image having the same color arrangement as thepixel arrangement. The captured image (frames) output from the imagingelement 42 is temporarily stored (overwritten and saved) in the storageunit of the main control unit 26 or a RAW image storage area (not shown)of the storage unit 48 determined in advance through the main controlunit 26.

The main control unit 26 subjects the frames to various kinds of imageprocessing. The main control unit 26 has a white balance (WB) gain unit,a gamma correction unit, and a synchronization processing unit (all ofthese are not shown), and sequentially performs signal processing forthe original digital signals (RAW images) temporarily stored in the maincontrol unit 26 or the like in each processing unit. That is, the WBgain unit executes white balance (WB) adjustment by adjusting the gainof each of R, G, and B signals. The gamma correction unit performs gammacorrection of each of the R, G, and B signals subjected to the WBadjustment in the WB gain unit. The synchronization processing unitperforms color interpolation processing corresponding to the arrangementof the color filters of the imaging element 42 and generates thesynchronized R, G, and B signals. Each time the RAW image for one screenis acquired by the imaging element 42, the main control unit 26 performsimage processing for the RAW image in parallel.

The main control unit 26 outputs image data of the generated capturedimage for recording to an encoder (not shown), which converts an inputsignal to a signal in a different format. The R, G, and B signalsprocessed by the main control unit 26 are converted (encoded) to signalsfor recording by the encoder, and the signals for recording are recordedin the storage unit 48. The captured image for display processed by themain control unit 26 is output to the view finder 46.

The main control unit 26 of this embodiment displays a live view imageon the view finder 46 by performing control for continuously displayingthe captured images for display as a motion image.

The light emitting lens 30 and the laser diode 32 function as an exampleof an emission unit. The laser diode 32 is driven based on aninstruction from the distance measurement control unit 24 and has afunction of emitting a laser beam toward the subject to be a measurementtarget through the light emitting lens 30 in the optical axis directionof the imaging optical system 40. Specific examples of the lightemitting lens 30 of this embodiment include an objective lens or thelike. The laser beam emitted from the laser diode 32 is an example ofdirectional light according to the technique of the present disclosure.

The light receiving lens 34 and the photodiode 36 function as an exampleof a light receiving unit. The photodiode 36 has a function of receivingthe laser beam emitted from the laser diode 32 and reflected from thesubject through the light receiving lens 34 and outputting an electricalsignal according to the amount of received light to the distancemeasurement control unit 24.

If the user provides an instruction for a distance measurement using thedistance measurement imaging start button, the release button, or thedistance measurement instruction button, or the like of the operatingunit 44, the main control unit 26 instructs the distance measurementcontrol unit 24 for a distance measurement. Specifically, in thisembodiment, the main control unit 26 instructs the distance measurementcontrol unit 24 to start a distance measurement by transmitting adistance measurement instruction signal to the distance measurementcontrol unit 24. In a case of performing a measurement of a distance toa subject and imaging of the subject together, the main control unit 26transmits a synchronization signal for synchronizing a distancemeasurement operation and an imaging operation to the distancemeasurement control unit 24 as the distance measurement instructionsignal.

If the distance measurement instruction signal are received, thedistance measurement control unit 24 controls the light emission of thelaser diode 32 at the timing according to the count signal of the timecounter 22 and controls the timing of emitting a laser beam toward thesubject. The distance measurement control unit 24 samples the electricsignal according to the amount of received light output from thephotodiode 36 at the timing according to the count signal of the timecounter 22.

The distance measurement control unit 24 derives the distance to thesubject based on the light emission timing at which the laser diode 32emits a laser beam and the light reception timing at which thephotodiode 36 receives the laser beam, and outputs distance datarepresenting the derived distance to the main control unit 26. The maincontrol unit 26 displays information relating to the distance to thesubject on the view finder 46 based on distance data. The main controlunit 26 stores distance data in the storage unit 48.

The measurement of the distance to the subject by the distancemeasurement control unit 24 will be described in more detail. FIG. 2 isa timing chart showing an example of the timing of the distancemeasurement operation in the measurement of the distance to the subjectin the distance measurement device 10.

In the distance measurement device 10 of this embodiment, a singledistance measurement (measurement) sequence includes a voltageadjustment period, an actual measurement period, and a pause period. Thevoltage adjustment period refers to a period during which a drivevoltage of the laser diode 32 and the photodiode 36 is adjusted to anappropriate voltage value. As a specific example, in the distancemeasurement device 10 of this embodiment, as shown in FIG. 2, thevoltage adjustment period is set to several 100 msec (milliseconds).

The actual measurement period refers to a period in which the distanceto the subject is actually measured. In the distance measurement device10 of this embodiment, as a specific example, as shown in FIG. 2, thedistance to the subject is measured by repeating an operation to emit alaser beam and to receive the laser beam reflected from the subjectseveral 100 times and measuring the elapsed time from light emission tolight reception. That is, in the distance measurement device 10 of thisembodiment, in the single measurement sequence, the measurement of thedistance to the subject is performed several 100 times.

FIG. 3 is an example of a timing chart showing the timing from lightemission to light reception in a single measurement. In a case ofperforming a distance measurement, the distance measurement control unit24 outputs a laser trigger for causing the laser diode 32 to emit lightaccording to the count signal of the time counter 22 to the laser diode32. The laser diode 32 emits light according to the laser trigger. Inthe distance measurement device 10 of this embodiment, as a specificexample, the light emission time of the laser diode 32 is set to several10 nsec (nanoseconds). The emitted laser beam is emitted toward thesubject through the light emitting lens 30 in the optical axis directionof the imaging optical system 40. The laser beam emitted from thedistance measurement device 10 is reflected from the subject and reachesthe distance measurement device 10. The photodiode 36 of the distancemeasurement device 10 receives the reflected laser beam through thelight receiving lens 34.

In the distance measurement device 10 of this embodiment, as a specificexample, the distance measurement device performs a distance measurementfor a subject within several km from the distance measurement device 10.The time until the laser beam emitted from the laser diode 32 toward thesubject several km ahead through the light emitting lens 30 is returned(received) becomes several km×2/light speed=several μsec (microseconds).Accordingly, in order to measure the distance to the subject several kmahead, as an example, as shown in FIG. 2, the time of at least severalμsec is required.

In the distance measurement device 10 of this embodiment, thereciprocation time or the like of the laser beam is considered, and as aspecific example, a single measurement time is set to several msec asshown in FIG. 2. Since the reciprocation time of the laser beam isdifferent depending on the distance to the subject, the measurement timefor each time may be different depending on the distance assumed by thedistance measurement device 10.

In the distance measurement device 10, the distance measurement controlunit 24 derives the distance to the subject based on measured valuesobtained by performing a measurement several 100 times as describedabove. In the distance measurement control unit 24 of this embodiment,as a specific example, a histogram of measured values for several 100times is analyzed to derive the distance to the subject. FIG. 4 is agraph showing an example of a histogram of measured values in a casewhere the distance to the subject is set as a horizontal axis and themeasurement frequency is set as a vertical axis. The distancemeasurement control unit 24 derives the distance to the subjectcorresponding to a maximum value of the measurement frequency in theabove-described histogram as a measurement result and outputs distancedata indicating the derived measurement result to the main control unit26. A histogram may be generated based on the reciprocation time (theelapsed time from light emission to light reception) of the laser beamor ½ of the reciprocation time of the laser beam, or the like, insteadof the distance to the subject.

The pause period refers to a period for pausing the driving of the laserdiode 32 and the photodiode 36. In the distance measurement device 10 ofthis embodiment, as a specific example, as shown in FIG. 2, the pauseperiod is set to several 100 msec.

In the distance measurement device 10 of this embodiment, the singlemeasurement time is set to several 100 msec.

The main control unit 26 of the distance measurement device 10 of thisembodiment displays a live view image on the view finder 46 as describedabove. The main control unit 26 performs the display of the live viewimage by displaying the captured images captured in several 10 fps(several 10 msec/image) on the view finder 46 as a motion image. Forthis reason, during the single measurement period, live view images forseveral 10 are displayed on the view finder 46.

The live view image is displayed on the view finder 46 in this way,whereby it is possible to perform the distance measurement whileconfirming the subject. However, if transition is made to a state wherethe actual exposure is possible for still image capture before thedistance measurement to the subject is finished, the live view imagecannot be temporarily displayed. For this reason, it is not possible toperform the distance measurement while confirming the subject.

Accordingly, in the distance measurement device 10 according to thisembodiment, in a case of performing the distance measurement, the liveview image is displayed on the view finder 46. Then, the main controlunit 26 performs control such that transition is made to a state wherethe actual exposure for still image capture is possible at the timing ofthe end of the distance measurement. Here, “the timing of the end of thedistance measurement” indicates the end timing of all of several 100 ofmeasurements of the emission and the reception of the laser beam for thedistance measurement, the timing of the end of the measurement, thetiming of deriving the distance after the measurement, or the timingbefore and after the end of derivation of the distance.

Next, an imaging operation and a distance measurement operation in thedistance measurement device 10 of this embodiment will be described. Inthe following description, an imaging operation and a distancemeasurement operation in a case of performing an imaging operation and adistance measurement operation to capture a still image will bedescribed.

First, control processing which is executed by the main control unit 26in a case where a distance measurement imaging start button is providedin the operating unit 44. FIG. 5 is a flowchart showing an example of aflow of control processing which is executed by the main control unit 26in a case where the distance measurement imaging start button isprovided in the operating unit 44 in the distance measurement device 10of this embodiment. The flowchart shown in FIG. 5 is executed if poweris supplied to the distance measurement device 10.

First, in Step 100, the main control unit 26 starts a live viewoperation. As described above, the main control unit 26 displays thelive view image on the view finder 46 by performing control forcontinuously displaying the captured images obtained by the imagingoptical system 40 and the imaging element 42 as a motion image.

Next, in Step 102, the main control unit 26 determines whether or notthe distance measurement imaging start button of the operating unit 44is operated. In a case where the distance measurement imaging startbutton is not operated, the process progresses to Step 126. In a casewhere the distance measurement imaging start button is operated, theprocess progresses to Step 104.

In Step 104, the main control unit 26 starts a distance measurementtimer. The distance measurement timer is a timer for measuring thetiming of the end of the distance measurement, and measures apredetermined time required for several 100 of measurements describedabove. The distance measurement timer is a timer for measuring thetiming the end of the distance measurement, and may measure the timecorresponding to a period toward the end of several 100 times, not thetime until several 100 of measurements completely end. Alternatively,the time until the timing before and after the end of a derivationperiod for deriving the distance after several 100 of measurements endmay be measured.

Next, in Step 106, the main control unit 26 transmits thesynchronization signal to the distance measurement control unit 24. Inthe distance measurement device 10 of this embodiment, In order tosynchronize the imaging operation by the main control unit 26 and thedistance measurement operation by the distance measurement control unit24, the synchronization signal is transmitted from the main control unit26 to the distance measurement control unit 24 prior to the start ofimaging (the actual exposure to the imaging element 42). Though detailswill be described below, in the distance measurement control unit 24, ifthe synchronization signal is received, the distance measurementoperation (the measurement of the distance to the subject) starts.

Next, in Step 108, the main control unit 26 controls the imaging opticalsystem 40 and performs AE and AF as described above. In the distancemeasurement device 10, exposure adjustment is performed by performingAE, focus adjustment is performed by performing AF, and image lightindicating the subject is formed on the light receiving surface of theimaging element 42 in a focused state.

Next, in Step 109, the main control unit 26 determines whether or not anerror of AE or AF occurs. In a case where an error occurs, thedetermination is affirmative and the process returns to Step 108. In acase where no error occurs, the determination is negative and theprocess progresses to Step 110.

In Step 110, the main control unit 26 transmits exposure statespecification information for specifying an exposure state at thepresent time as a result of AE to the distance measurement control unit24. In Step 110, the main control unit 26 also transmits focusing statespecification information for specifying a focusing state at the presenttime as a result of AF to the distance measurement control unit 24.Examples of the exposure state specification information include anF-number and a shutter speed uniquely determined according to subjectbrightness, an F-number and a shutter speed derived from a so-called AEevaluation value uniquely determined according to subject brightness, orthe like. Other examples of the exposure state specification informationinclude an AE evaluation value. Examples of the focusing statespecification information include the subject distance obtained by AF.Hereinafter, for convenience of description, in a case where there is noneed for distinction between the exposure state specificationinformation and the focusing state specification information, these arereferred to as “specification information”.

Next, in Step 112, the main control unit 26 determines whether or not adistance measurement end time is reached. That is, it is determinedwhether or not the distance measurement timer times up. The main controlunit 26 is in a standby state until the distance measurement end time isreached, and in a case where the distance measurement end time isreached, progresses to Step 114. That is, in a case where the distancemeasurement end time is reached, the emission of the laser diode 32 andthe reception of the photodiode 36 are paused.

In Step 114, the main control unit 26 starts the actual exposure(imaging). With the start of the actual exposure, the pixels of theimaging element 42 are irradiated with light (image light is formed onthe light receiving surface of the imaging element 42), and signalcharges according to irradiated light are stored in the respectivepixels. That is, in a case where the distance measurement end time isreached, since the light emission of the laser diode 32 and thereception of the photodiode 36 are paused, it is possible to preventnoise caused by the laser beam from being superimposed on a capturedimage even if the actual exposure is performed.

Next, in Step 116, the main control unit 26 detects whether or not theactual exposure ends. The main control unit 26 is in a standby stateuntil the actual exposure ends, and in a case where the actual exposureends, progresses to Step 118. A determination method regarding whetheror not the actual exposure ends is not limited, and as a specificexample, a method which determines the end of the actual exposure bydetermining whether or not an actual exposure time determined undervarious conditions elapses is considered.

In Step 118, the main control unit 26 starts the reading of the signalcharges stored in the respective pixels of the imaging element 42.

Next, in Step 120, the main control unit 26 determines whether or not toend the reading. In a case where the signal charges are not yet readfrom all pixels of the imaging element 42, the main control unit 26performs the determination of Step 120 again. In a case where the signalcharges are read from all pixels of the imaging element 42, the processprogresses to Step 122.

Next, in Step 122, the main control unit 26 determines whether or notdistance data is received. Though details will be described below, ifthe distance measurement is performed, the distance measurement controlunit 24 transmits distance data indicating a distance measurement result(finally derived distance) to the main control unit 26. The main controlunit 26 is in a standby state until distance data transmitted from thedistance measurement control unit 24 is received, and in a case wheredistance data is received, progresses to Step 124.

In Step 124, the main control unit 26 displays information relating tothe distance to the subject on the view finder 46 based on receiveddistance data so as to be superimposed on a live view image. The maincontrol unit 26 stores received distance data in the storage unit 48 incorrelation with a captured image obtained by imaging. With this step,the captured image (image data indicating the captured image) obtainedby imaging the subject and the distance (distance data) to the subjectare stored in the storage unit 48 in correlation with each other.

In Step 126, the main control unit 26 determines whether or not a powerswitch (not shown) is turned off. In a case where the power switch isnot turned off, the process returns to Step 102, and this processing isrepeated. In a case where the power supply is turned off, the processprogresses to Step 128.

In Step 128, the main control unit 26 stops the live view operation, andthen, ends this processing. The main control unit 26 turns off the powersupply of the distance measurement device 10.

Next, distance measurement processing which is executed by the distancemeasurement control unit 24 in a case where a distance measurementimaging start button is provided in the operating unit 44 will bedescribed. FIG. 6 is a flowchart showing an example of a flow ofdistance measurement processing which is executed by the distancemeasurement control unit 24 in a case where the distance measurementimaging start button is provided in the operating unit 44 in thedistance measurement device 10 of this embodiment. The flowchart shownin FIG. 6 is executed if power is supplied to the distance measurementdevice 10.

First, in Step 150, the distance measurement control unit 24 determineswhether or not the synchronization signal is received. Specifically, thedistance measurement control unit 24 determines whether or not thesynchronization transmitted from the main control unit 26 in Step 106 ofthe control processing in the main control unit 26 described above isreceived. The distance measurement control unit 24 is in a standby stateuntil the synchronization signal is received, and if the synchronizationsignal is received, the process progresses to Step 152.

In Step 152, the distance measurement control unit 24 determines whetheror not the specification transmitted in Step 110 of the controlprocessing described above is received. In Step 152, in a case where thespecification information is not received, the determination isnegative, and the distance measurement control unit 24 performs thedetermination of Step 152 again. In Step 152, in a case where thespecification information is received, the determination is affirmativeand the process progresses to Step 154.

In Step 154, the distance measurement control unit 24 determines theeffective distance measurement range (an example of a distance rangeaccording to the present disclosure) based on the focusing statespecification information received in Step 152. For example, thedistance measurement control unit 24 determines the effective distancemeasurement range with reference to a range derivation table (not shown)in which the effective distance measurement range is uniquely derivedfrom the focusing state specification information.

The effective distance measurement range is a distance range which isused when determining the frequency of each of the distances obtained bydriving the distance to the subject multiple times. That is, theeffective distance measurement range indicates an effective range of adistance to be derived in Step 170 described below and means the rangeof the subject distance and the vicinity thereof estimated from thefocusing state specification information.

Examples of the range derivation table include a table in which a movingdirection and a moving distance of a focus lens from a referenceposition determined in advance are correlated with an effective distancemeasurement range. The moving direction and the moving distance arespecified by the focusing state specification information.

The distance measurement control unit 24 may determine the effectivedistance measurement range using an arithmetic expression with thefocusing state specification information as an independent variable andthe effective distance measurement range as a dependent variable aswithout using the range derivation table.

Next, in Step 156, the distance measurement control unit 24 determines aderivation resolution uniquely determined from the effective distancemeasurement range determined in Step 154.

The derivation resolution is a resolution increased according to theeffective distance measurement range determined in Step 154 and is setto be higher than a predetermined resolution. The predeterminedresolution used herein indicates, for example, a resolution which isused in a case of performing a distance measurement (in a case ofderiving the distance to the subject) without being bound by theeffective distance measurement range. In this embodiment, as an exampleof the derivation resolution, a resolution which is set to be higherthan the predetermined resolution using a number of bits (for example, 8bits) determined in advance as the number of bits defining thepredetermined resolution is used.

In this embodiment, although the effective distance measurement range isdetermined to set the derivation resolution, the distance measurementmay be performed without determining the effective distance measurementrange. That is, Step 110 in the main control unit 26 and Steps 154 and156 in the distance measurement control unit 24 may be omitted.

Next, in Step 158, the distance measurement control unit 24 transitionsto the voltage adjustment period and performs voltage adjustment of thedrive voltage of the laser diode 32 and the photodiode 36, whereby theemission intensity of the laser beam of the laser diode 32 is adjustedand the light receiving sensitivity of the photodiode 36 is adjusted.

The emission intensity of the laser beam emitted from the laser diode 32is adjusted based on the specification information received in Step 152.For example, the distance measurement control unit 24 adjusts theemission intensity of the laser beam with reference to an intensitysetting table (not shown) in which voltage information indicating thedrive voltage of the laser diode 32 is uniquely derived from thespecification information. That is, the distance measurement controlunit 24 derives the voltage information corresponding to thespecification information received in Step 152 from the intensitysetting table and performs the voltage adjustment such that the drivevoltage indicated by the derived voltage information is applicable tothe laser diode 32 (see FIG. 19).

Examples of the intensity setting table include a table in which voltageinformation representing the shorter a distance to a principal subject,the lower the emission intensity of the laser beam, and the smaller theamount of ambient light (the lower the subject brightness or the higherthe exposure), the lower the emission intensity of the laser beam isstored. The distance to the principal subject is specified by thefocusing state specification information, and the amount of ambientlight is specified by the subject brightness or the exposure statespecification information. Ambient light becomes noise for the laserbeam, and this means that the smaller the amount of ambient light, thesmaller the noise of the laser beam becomes. Accordingly, in Step 158,the distance measurement control unit 24 performs the voltage adjustmentsuch that the emission intensity of the laser beam becomes small in acase where the amount of ambient light is small.

The distance measurement control unit 24 may adjust the emissionintensity of the laser beam based on the voltage information derived byan arithmetic expression with the exposure state specificationinformation and the focusing state specification information asindependent variables and the voltage information as a dependentvariable without using the intensity setting table.

Here, although a case where the emission intensity of the laser beam isadjusted based on the exposure state specification information and thefocusing state specification information received in Step 152 has beenillustrated, the embodiment is not limited thereto. For example, theemission intensity of the laser beam may be adjusted based on theexposure state specification information or the focusing statespecification information.

The light receiving sensitivity of the photodiode 36 is adjusted basedon the focusing state specification information received in Step 152.For example, the distance measurement control unit 24 adjusts the lightreceiving sensitivity of the photodiode 36 with reference to asensitivity adjustment table (not shown) in which the voltageinformation indicating the drive voltage of the photodiode 36 isuniquely derived from the specification information. That is, thedistance measurement control unit 24 derives the voltage informationcorresponding to the focusing state specification information receivedin Step 152 from the sensitivity adjustment table. Then, the voltageadjustment is performed such that the drive voltage indicated by thederived voltage information is applicable to the photodiode 36 (see FIG.19).

Examples of the sensitivity adjustment table include a table in whichvoltage information representing the shorter the distance to theprincipal subject, the lower the light receiving sensitivity of thephotodiode 36 is stored.

The distance measurement control unit 24 may set the light receivingsensitivity of the photodiode 36 based on voltage information derived byan arithmetic expression with the focusing state specificationinformation as an independent variable and the voltage information as adependent variable without using the sensitivity adjustment table.

In Step 160, the distance measurement control unit 24 determines whetheror not the voltage adjustment ends. In this embodiment, as an example,as shown in FIG. 2, the voltage adjustment period is set to several 100msec. For this reason, the distance measurement control unit 24determines that the voltage adjustment ends in a case where several 100msec have elapsed after the transition to the voltage adjustment period.Accordingly, the distance measurement control unit 24 determines thatthe voltage adjustment does not end and is in a standby state untilseveral 100 msec have elapsed after the transition to the voltageadjustment period, and in a case where several 100 msec have elapsed,determines that the voltage adjustment ends and progresses to Step 164.

Next, in Step 164, the distance measurement control unit 24 causes thelaser diode 32 to emit light such that a laser beam having emissionintensity adjusted in Step 158 is emitted.

Next, in Step 166, the distance measurement control unit 24 determineswhether or not a predetermined time has elapsed. Specifically, asdescribed above, since the single measurement time is set to severalmsec, the distance measurement control unit 24 determines whether or notseveral msec have elapsed. In a case where the predetermined time (inthis embodiment, several msec which are the single measurement time) hasnot elapsed, the process is in the standby state, and in a case wherethe predetermined time has elapsed, the process progresses to Step 168.

The laser diode 32 emits light through the processing of Step 164,whereby the laser beam is emitted toward the subject through the lightemitting lens 30. The laser beam reflected from the subject is receivedby the photodiode 36 through the light receiving lens 34 until thepredetermined time elapses. The distance measurement control unit 24acquires the elapsed time from light emission to light reception in acase where the laser beam is received by the photodiode 36 and storesthe elapsed time in the storage unit (for example, the RAM or the likein the distance measurement control unit 24).

For example, in a case where the subject moves, or the like, the elapsedtime from light emission to light reception of the laser beam exceedsseveral msec, and the laser beam may not be returned (reflected lightmay not be received). In this case, a measurement error occurs. In acase where a measurement error occurs, the distance measurement controlunit 24 stores the effect in the storage unit (for example, the RAM orthe like in the distance measurement control unit 24). Then, theoccurrence of the measurement error may be displayed on the view finder46 or the like according to the frequency of the occurrence of themeasurement error, for example, if the frequency is not negligible inderiving the distance to the subject using a histogram. In this way, ina case where a measurement error occurs, the main control unit 26 maynot store the captured image in the storage unit 48. In this case, theuser can set whether or not to store the captured image.

Next, in Step 168, the distance measurement control unit 24 determineswhether or not a predetermined number of measurements end. In Step 168,in a case where a predetermined number of measurements end, thedetermination is affirmative, and the process progresses to Step 170. InStep 168, in a case where a predetermined number of measurements do notend, the determination is negative, and the process returns to Step 164.The predetermined number of measurements corresponds to several 100 ofmeasurements.

In Step 170, first, the distance measurement control unit 24 derives thedistance to the subject based on the time from when the laser beam isemitted through the processing of Step 164 until the photodiode 36receives the laser beam. As an example, as shown in FIG. 4, the distancemeasurement control unit 24 generates a histogram of the deriveddistance to the subject with the predetermined resolution. Next, as anexample, as shown in FIG. 4, the distance measurement control unit 24reconstructs a histogram of the distance to the subject using thederivation resolution derived within the effective distance measurementrange determined in the processing of Steps 154 and 156. The distancemeasurement control unit 24 analyzes the histogram within the effectivedistance measurement range and generates distance data representing theanalyzed distance (in the example shown in FIG. 4, the distance havingthe maximum measurement frequency). Here, the distance represented bydistance data is a final distance (final output) which is provided tothe user.

The histogram generated with the derivation resolution is segmented incontrast to the histogram generated with the predetermined resolution.Accordingly, the distance obtained by analyzing the histogram isexpressed in units of minute numerical values (units of smallernumerical values) in contrast to the distance obtained by analyzing thehistogram generated with the predetermined resolution.

Next, in Step 172, the distance measurement control unit 24 transmitsdistance data generated in Step 170 to the main control unit 26, andthen, the process progresses to Step 174.

In Step 174, the distance measurement control unit 24 determines whetheror not conditions (end conditions) determined in advance as conditionsfor ending this distance measurement processing are satisfied. Anexample of the end conditions is a condition that an end instructionfrom the user is received by the operating unit 44. In Step 174, in acase where the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 150. In Step 174, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this distance measurement processing ends.

As described above, in the distance measurement device 10 according tothis embodiment, in a case of performing the distance measurement to thesubject, the live view image is displayed on the view finder 46, andtransition is made to a state where the actual exposure is possible atthe timing of the end of the distance measurement to perform still imagecapture. With this, it is possible to prevent the subject from becomingnon-confirmable since the live view is not displayed during the distancemeasurement due to switching from live view imaging to still imagecapture at the start of the distance measurement.

Subsequently, control processing which is executed by the main controlunit 26 in a case where a release button is provided in the operatingunit 44 will be described. FIG. 7 is a flowchart showing an example of aflow of control processing which is executed by the main control unit 26in a case where the release button is provided in the operating unit 44in the distance measurement device 10 of this embodiment. The flowchartshown in FIG. 7 is executed if power is supplied to the distancemeasurement device 10. The same processing as that in the flowchart ofFIG. 5 which is executed by the main control unit 26 in a case where thedistance measurement imaging start button is provided in the operatingunit 44 is represented by the same reference numeral.

First, in Step 100, the main control unit 26 starts the live viewoperation. As described above, the main control unit 26 performs controlsuch that captured images captured by the imaging optical system 40 andthe imaging element 42 are successively displayed as a motion image,thereby displaying a live view image on the view finder 46.

Next, in Step 101, the main control unit 26 determines whether or notthe release button of the operating unit 44 is half-pressed. In a casewhere the release button is not half-pressed, for example, in a casewhere the release button is not pressed at all, or the like, the processprogresses to Step 126. In a case where the release button ishalf-pressed, the process progresses to Step 104.

In Step 104, the main control unit 26 starts the distance measurementtimer. The distance measurement timer is a timer for measuring thetiming of the end of the distance measurement, and measures apredetermined time required for several 100 of measurements describedabove. The distance measurement timer is a timer for measuring thetiming the end of the distance measurement, and may measure the timecorresponding to a period toward the end of several 100 times, not thetime until several 100 of measurements completely end. Alternatively,the time until the timing of the end of the derivation period forderiving the distance after several 100 of measurements end may bemeasured.

Next, in Step 106, the main control unit 26 transmits thesynchronization signal to the distance measurement control unit 24. Inthis way, in the distance measurement device 10 of this embodiment, inorder to synchronize the imaging operation by the main control unit 26and the distance measurement operation by the distance measurementcontrol unit 24, the synchronization signal is transmitted from the maincontrol unit 26 to the distance measurement control unit 24 prior to thestart of imaging (the actual exposure to the imaging element 42). Thoughdetails will be described below, in the distance measurement controlunit 24, if the synchronization signal is received, the distancemeasurement operation (the measurement of the distance to the subject)starts.

Next, in Step 108, the main control unit 26 controls the imaging opticalsystem 40 and performs AE and AF as described above. In the distancemeasurement device 10, exposure adjustment is performed by performingAE, focus adjustment is performed by performing AF, and image lightindicating the subject is formed on the light receiving surface of theimaging element 42 in a focused state.

Next, in Step 109, the main control unit 26 determines whether or not anerror of AE or AF occurs. In a case where an error occurs, thedetermination is affirmative and the process returns to Step 108. In acase where no error occurs, the determination is negative and theprocess progresses to Step 110.

In Step 110, the main control unit 26 transmits the exposure statespecification information for specifying the exposure state at thepresent time as a result of AE to the distance measurement control unit24. In Step 110, the main control unit 26 also transmits the focusingstate specification information for specifying the focusing state at thepresent time as a result of AF to the distance measurement control unit24.

Next, in Step 112, the main control unit 26 determines whether or not adistance end time is reached. That is, it is determined whether or notthe distance measurement timer times up. The main control unit 26 is ina standby state until the distance measurement end time is reached, andin a case where the distance measurement end time is reached, progressesto Step 113.

Next, in Step 113, the main control unit 26 determines whether or notthe release button of the operating unit 44 is fully pressed. In a casewhere the release button is not fully pressed, the process progresses toStep 115.

In Step 115, the main control unit 26 determines whether or not apressing operation to the release button of the operating unit 44 isreleased. In a case where pressing is not released, the process returnsto Step 113, and this processing is repeated. In a case where pressingis released, the process progresses to Step 122.

In a case where the release button is fully pressed, the processprogresses from Step 113 to Step 114.

Next, in Step 114, the main control unit 26 starts the actual exposure(imaging). With the start of the actual exposure, the pixels of theimaging element 42 are irradiated with light (image light is formed onthe light receiving surface of the imaging element 42), and signalcharges according to irradiated light are stored in the respectivepixels. That is, in a case where the distance measurement end time isreached and the release button is fully pressed, the emission of thelaser diode 32 and the reception of the photodiode 36 are paused.Accordingly, it is possible to prevent noise caused by the laser beamfrom being superimposed on a captured image even if the actual exposureis performed.

Next, in Step 116, the main control unit 26 detects whether or not theactual exposure ends. The main control unit 26 is in a standby stateuntil the actual exposure ends, and in a case where the actual exposureends, progresses to Step 118. A determination method regarding whetheror not the actual exposure ends is not limited, and as a specificexample, a method which determines the end of the actual exposure bydetermining whether or not an actual exposure time determined undervarious conditions elapses is considered.

In Step 118, the main control unit 26 starts the reading of the signalcharges stored in the respective pixels of the imaging element 42.

Next, in Step 120, the main control unit 26 determines whether or not toend the reading. In a case where the signal charges are not yet readfrom all pixels of the imaging element 42, the main control unit 26performs the determination of Step 120 again. In a case where the signalcharges are read from all pixels of the imaging element 42, the processprogresses to Step 122.

Next, in Step 122, the main control unit 26 determines whether or notdistance data is received. If the distance measurement is performed, thedistance measurement control unit 24 transmits distance data indicatinga distance measurement result (finally derived distance) to the maincontrol unit 26. The main control unit 26 is in a standby state untildistance data transmitted from the distance measurement control unit 24is received, and in a case where distance data is received, progressesto Step 124.

In Step 124, the main control unit 26 displays information relating tothe distance to the subject on the view finder 46 based on receiveddistance data so as to be superimposed on a live view image. The maincontrol unit 26 stores received distance data in the storage unit 48 incorrelation with a captured image obtained by imaging. With this step,the captured image (image data indicating the captured image) obtainedby imaging the subject and the distance (distance data) to the subjectare stored in the storage unit 48 in correlation with each other.

In Step 126, the main control unit 26 determines whether or not a powerswitch (not shown) is turned off. In a case where the power switch isnot turned off, the process returns to Step 102, and this processing isrepeated. In a case where the power supply is turned off, the processprogresses to Step 128.

In Step 128, the main control unit 26 stops the live view operation, andthen, ends this processing. The main control unit 26 turns off the powersupply of the distance measurement device 10.

Distance measurement processing which is executed by the distancemeasurement control unit 24 in a case where a release button is providedin the operating unit 44 is the same as the distance measurementprocessing which is executed by the distance measurement control unit 24in a case where a distance measurement imaging start button is providedin the operating unit 44, and thus, description thereof will not berepeated.

In this way, the processing in a case where a release button is providedin the operating unit 44 is the same as in a case where a distancemeasurement imaging start button is provided in the operating unit 44.That is, in a case of performing the distance measurement to thesubject, the live view image is displayed on the view finder 46, andtransition is made to a state where the actual exposure is possible atthe timing of the end of the distance measurement to perform still imagecapture. With this, it is possible to prevent the subject from becomingnon-confirmable since the live view is not displayed during the distancemeasurement due to switching from live view imaging to still imagecapture at the start of the distance measurement.

Subsequently, a modification example of the respective processing whichis executed by each of the main control unit 26 and the distancemeasurement control unit 24 of the distance measurement device 10according to this embodiment will be described.

In the foregoing embodiment, an example where the main control unit 26detects the timing of the end of the distance measurement using thedistance measurement timer and transitions to a state where the actualexposure is possible has been described. In contrast, in a modificationexample, an example where the main control unit 26 receives a distancemeasurement end signal representing the timing of the end of thedistance measurement from the distance measurement control unit 24without using the distance measurement timer, and transitions to a statewhere the actual exposure is possible is provided.

First, a modification example of the control processing which isexecuted by the main control unit 26 in a case where the distancemeasurement imaging start button is provided in the operating unit 44will be described. FIG. 8 is a flowchart showing a modification exampleof the flow of the control processing which is executed by the maincontrol unit 26 in a case where the distance measurement imaging startbutton is provided in the operating unit 44 in the distance measurementdevice 10 of this embodiment. The flowchart shown in FIG. 8 is executedif power is supplied to the distance measurement device 10. The sameprocessing as that in the flowchart of FIG. 5 is represented by the samereference numeral, and description thereof will not be repeated.

As shown in FIG. 8, the modification example is different from theforegoing embodiment only in that Step 104 of FIG. 5 is omitted and Step111 is performed instead of Step 112.

That is, instead of measuring the timing of the end of the distancemeasurement using the timer, in Step 111, it is determined whether ornot the distance measurement end signal is received from the distancemeasurement control unit 24, if the distance measurement end signal isreceived, the process progresses to Step 114, and the actual exposure isstarted. In the subsequent processing, the same processing as that inthe foregoing embodiment may be performed.

Next, a modification example of the distance measurement processingwhich is executed by the distance measurement control unit 24 in a casewhere the distance measurement imaging start button is provided in theoperating unit 44 will be described. FIG. 9 is a flowchart showing amodification example of the flow of the distance measurement processingwhich is executed by the distance measurement control unit 24 in a casewhere the distance measurement imaging start button is provided in theoperating unit 44 in the distance measurement device 10 of thisembodiment. The flowchart shown in FIG. 9 is executed if power issupplied to the distance measurement device 10. The same processing asthat in the flowchart of FIG. 6 is represented by the same referencenumeral, and description thereof will not be repeated.

As shown in FIG. 9, the modification example is different from theforegoing embodiment only in that Step 169 is further provided betweenStep 168 and Step 170 of FIG. 6.

That is, in Step 168, in a case where the predetermined number ofmeasurements end, the process progresses to Step 169. In Step 169, thedistance measurement control unit 24 transmits the distance measurementend signal to the main control unit 26 and progresses to Step 170. Withthis, the determination of Step 111 described above is affirmative.Here, the distance measurement control unit 24 determines the completionof a predetermined number of receptions of the emitted signals as thetiming of the end of the distance measurement and transmits the distancemeasurement end signal representing that the distance measurement ends.With this, in a case where the distance measurement end signal isreceived, the determination of Step 111 is affirmative, and the maincontrol unit 26 receives the emitted laser beam accurately, determinesthat the distance is derived, and starts the actual exposure. Step 169may be performed after the distance derivation in next Step 170. In theprocessing after Step 170, the same processing as that in the foregoingembodiment may be performed.

Even if the processing is performed as described above, in a case ofperforming the distance measurement to the subject, the live view imagecan be displayed on the view finder 46, and transition can be made to astate where the actual exposure is possible at the timing of the end ofthe distance measurement to perform still image capture. With this, itis possible to prevent the subject from becoming non-confirmable sincethe live view is not displayed during the distance measurement due toswitching from live view imaging to still image capture at the start ofthe distance measurement.

Subsequently, a modification example of the control processing which isexecuted by the main control unit 26 in a case where the release buttonis provided in the operating unit 44 will be described. FIG. 10 is aflowchart showing a modification example of the flow of the controlprocessing which is executed by the main control unit 26 in a case wherethe release button is provided in the operating unit 44 in the distancemeasurement device 10 of this embodiment. The flowchart shown in FIG. 10is executed if power is supplied to the distance measurement device 10.The same processing as that in the flowchart of FIG. 7 is represented bythe same reference numeral, and description thereof will not berepeated.

As shown in FIG. 10, the modification example is different from theforegoing embodiment only in that Step 104 of FIG. 7 is omitted and Step111 is performed instead of Step 112.

That is, instead of measuring the timing of the end of the distancemeasurement using the timer, in Step 111, it is determined whether ornot the distance measurement end signal is received from the distancemeasurement control unit 24. Then, if the distance measurement endsignal is received, the process progresses to Step 113 and it isdetermined whether or not the release button of the operating unit 44 isfully pressed. In the subsequent processing, the same processing as thatin the foregoing embodiment may be performed.

A modification example of the distance measurement processing which isexecuted by the distance measurement control unit 24 in a case where therelease button is provided in the operating unit 44 is the same as themodification example of the distance measurement processing which isexecuted by the distance measurement control unit 24 in a case where thedistance measurement imaging start button is provided in the operatingunit 44, and thus, description thereof will not be repeated.

Even if the processing is performed as described above, in a case ofperforming the distance measurement to the subject, the live view imagecan be displayed on the view finder 46, and transition can be made to astate where the actual exposure is possible at the timing of the end ofthe distance measurement to perform still image capture. With this, itis possible to prevent the subject from becoming non-confirmable sincethe live view is not displayed during the distance measurement due toswitching from live view imaging to still image capture at the start ofthe distance measurement.

On the other hand, in the distance measurement control unit 24, theremay occur a case where the distance to the subject cannot be measured(distance measurement error). In this case, in the modificationexamples, the main control unit 26 may end the processing withouttransitioning to the actual exposure of still image capture.Alternatively, the main control unit 26 may stop storage in the storageunit 48 to prevent storage of an incomplete captured image with nodistance data. FIG. 11A is a flowchart showing an example of distancemeasurement error processing of the distance measurement control unit24. FIG. 11B is a flowchart showing an example of distance measurementerror processing of the main control unit 26 in a case where a distancemeasurement error occurs before transition to still image capture(actual exposure) (when the distance measurement end signal isreceived). FIG. 11C is a flowchart showing an example of distancemeasurement error processing of the main control unit 26 in a case wherea distance measurement error occurs after still image capture (whendistance data is received).

The distance measurement control unit 24 starts the distance measurementerror processing, for example, as interrupt processing in a case wheresignal transmission or reception is impossible or in a case where thedistance cannot be derived.

In the distance measurement error processing, in Step 200, the distancemeasurement control unit 24 determines whether or not it is a distancemeasurement error. In a case where no distance measurement error occurs,the determination is negative and the processing ends as it is. In acase where a distance measurement error occurs, the determination isaffirmative and the process progresses to Step 202.

In Step 202, the distance measurement control unit 24 transmits adistance measurement error signal to the main control unit 26 to end theprocessing.

In a case where a distance measurement error occurs before transition tostill image capture (for example, when the distance measurement endsignal is received in Step 111 or when the distance measurement end timeis reached in Step 112), in Step 230, the main control unit 26determines whether or not it is a distance measurement error. That is,it is determined whether or not the distance measurement error signal isreceived from the distance measurement control unit 24. In a case wherethe distance measurement error signal is not received, the determinationis negative, and the process progresses to the actual exposure of Step114 described above. Or, the process progresses to the determination offull pressing of Step 113 described above.

In a case where the distance measurement error signal is received, thedetermination is affirmative, in Step 232, an error is reported, and theprocess returns to Step 102 or Step 101. As the error report, forexample, a display representing that the distance measurement cannot beperformed is performed. Alternatively, an error may be reported by soundor the like or may be reported by display and sound. In a case where adistance measurement error occurs, a need for the actual exposure asstill image capture may be set in advance by the operating unit 44. Withthis, it is possible to arbitrarily set whether or not to perform stillimage capture in a case where the distance measurement is impossible.

In a case where a distance measurement error occurs after still imagecapture (when distance data is received in Step 122), in Step 250, themain control unit 26 determines whether or not it is a distancemeasurement error. That is, it is determined whether or not the distancemeasurement error signal is received from the distance measurementcontrol unit 24. In a case where the distance measurement error signalis not received, the determination is negative, and the processprogresses to the display and storage of distance data of Step 124described above.

In a case where the distance measurement error signal is received, thedetermination is affirmative, the process progresses to Step 252, andstorage of distance data and the captured image are stopped, and theprocess returns to the original processing (Step 126). In a case where adistance measurement error occurs, a need for storage of a still imageobtained by the actual exposure may be set in advance by the operatingunit 44. With this, it is possible to arbitrarily set whether or not tostore still image in a case where the distance measurement isimpossible.

In the foregoing embodiment and modification examples, when the maincontrol unit 26 performs the actual exposure in Step 114, focusadjustment for the actual exposure may be performed again. In this case,for example, the processing of Step 122 may be performed instead ofSteps 112 and 111, and before transition to the actual exposure in Step114, the main control unit 26 may acquire distance measurement data andmay perform focus adjustment using the acquired distance measurementdata. With this, it is possible to reduce the time of focus adjustmentfor the actual exposure.

In the foregoing embodiment and modification examples, although a casewhere the light emission frequency of the laser beam is fixed to apredetermined number of times has been illustrated, the embodiment isnot limited thereto. Since ambient light becomes noise for the laserbeam, the light emission frequency of the laser beam may be a lightemission frequency determined according to subject brightness.

Hereinafter, an example of a way of determining the light emissionfrequency of the laser beam will be described.

The light emission frequency of the laser beam is derived from a lightemission frequency determination table 300 shown in FIG. 12 as anexample. In the light emission frequency determination table 300, thesubject brightness and the light emission frequency of the laser beamare correlated with each other such that the higher the subjectbrightness, the larger the light emission frequency of the laser beambecomes. That is, in the light emission frequency determination table300, the subject brightness has a magnitude relationship of L₁<L₂< . . .<L_(n), and the light emission frequency has a magnitude relationship ofN₁<N₂< . . . <N_(n).

In the distance measurement device 10, in order to realize thederivation of the light emission frequency of the laser beam by thelight emission frequency determination table 300, brightness informationtransmission processing (see FIG. 13) is executed by the main controlunit 26, and light emission frequency determination processing (see FIG.14) is executed by the distance measurement control unit 24.

First, the brightness information transmission processing which isexecuted by the main control unit 26 if the power switch of the distancemeasurement device 10 is turned on will be described referring to FIG.13.

In the brightness information transmission processing shown in FIG. 13,first, in Step 400, the main control unit 26 determines whether or notbrightness acquisition start conditions which are conditions forstarting acquisition of subject brightness are satisfied. An example ofthe brightness acquisition start conditions is a condition that therelease button is half-pressed. Another example of the brightnessacquisition start conditions is a condition that the captured image isoutput from the imaging element 42.

In Step 400, in a case where the brightness acquisition start conditionsare satisfied, the determination is affirmative, and the processprogresses to Step 402. In Step 400, in a case where the brightnessacquisition start conditions are not satisfied, the determination isnegative, and the process progresses to Step 406.

In Step 402, the main control unit 26 acquires the subject brightnessfrom the captured image, and then, the process progresses to Step 404.Here, although a case where the subject brightness is acquired from thecaptured image has been illustrated, the embodiment is not limitedthereto. For example, if a brightness sensor which detects subjectbrightness is mounted in the distance measurement device 10, the maincontrol unit 26 may acquire the subject brightness from the brightnesssensor.

In Step 404, the main control unit 26 transmits brightness informationindicating the subject brightness acquired in Step 402 to the distancemeasurement control unit 24, and then, the process progresses to Step406.

In Step 406, the main control unit 26 determines whether or not endconditions which are conditions for ending this brightness informationtransmission processing are satisfied. An example of the end conditionsis a condition that the power switch of the distance measurement device10 is turned off. In Step 406, in a case where the end conditions arenot satisfied, the determination is negative, and the process progressesto Step 400. In Step 406, in a case where the end conditions aresatisfied, the determination is affirmative, and this brightnessinformation transmission processing ends.

Next, the light emission frequency determination processing which isexecuted by the distance measurement control unit 24 if the power switchof the distance measurement device 10 is turned on will be describedreferring to FIG. 14.

In the light emission frequency determination processing shown in FIG.14, first, in Step 410, the distance measurement control unit 24determines whether or not the brightness information transmitted byexecuting the processing of Step 404 is received. In Step 410, in a casewhere the brightness information transmitted by executing the processingof Step 404 is not received, the determination is negative, and theprocess progresses to Step 416. In Step 410, in a case where thebrightness information transmitted by executing the processing of Step404 is received, the determination is affirmative, and the processprogresses to Step 412.

In Step 412, the distance measurement control unit 24 derives the lightemission frequency corresponding to the subject brightness indicated bythe brightness information received in Step 410 from the light emissionfrequency determination table 300, and then, the process progresses toStep 414.

In Step 414, the distance measurement control unit 24 stores the lightemission frequency derived in the processing of Step 412 in the storageunit 48, and then, the process progresses to Step 416. The lightemission frequency stored in the storage unit 48 by the processing ofStep 416 means “a predetermined number of times” in Step 168 of thedistance measurement processing shown in FIGS. 6 and 9.

In Step 416, the main control unit 26 determines whether or not endconditions which are conditions for ending this light emission frequencydetermination processing are satisfied. An example of the end conditionsis a condition that the power switch of the distance measurement device10 is turned off. In Step 416, in a case where the end conditions arenot satisfied, the determination is negative, and the process progressesto Step 410. In Step 416, in a case where the end conditions aresatisfied, the determination is affirmative, and this light emissionfrequency determination processing ends.

Next, another example of a way of determining the light emissionfrequency of the laser beam will be described.

As an example, the light emission frequency of the laser beam is derivedaccording to a light emission frequency determination table 500 shown inFIG. 15. In the light emission frequency determination table 500,exposure state specification information (E₁, E₂, . . . , E_(n))uniquely determined according to the subject brightness and the lightemission frequency (N₁, N₂, . . . , N_(n)) of the laser beam arecorrelated with each other. Here, the exposure state specificationinformation uniquely determined according to the subject brightnessmeans, for example, exposure state specification information indicatingthat, the higher the subject brightness, the lower the exposure becomes.

In a case of deriving the light emission frequency of the laser beamusing the light emission frequency determination table 500, exposurestate specification information transmission processing (see FIG. 16) isexecuted by the main control unit 26, and light emission frequencydetermination processing (see FIG. 17) is executed by the distancemeasurement control unit 24.

First, the exposure state specification information transmissionprocessing which is executed by the main control unit 26 if the powerswitch of the distance measurement device 10 is turned on will bedescribed referring to FIG. 16.

In the exposure state specification information transmission processingshown in FIG. 16, first, in Step 600, the main control unit 26determines whether or not the release button is half-pressed. In Step600, in a case where the release button is not half-pressed, thedetermination is negative, and the process progresses to Step 606. InStep 600, in a case where the release button is half-pressed, thedetermination is affirmative, and the process progresses to Step 602. InFIG. 16, although a case where the release button is provided in theoperating unit 44 has been described as an example, in a case where adistance measurement imaging start button is provided in the operatingunit 44, for example, Step 600 may be omitted, and in a case where poweris supplied, the processing may be started.

In Step 602, the main control unit 26 performs AE based on the subjectbrightness acquired from the captured image, and then, the processprogresses to Step 604.

In Step 604, the main control unit 26 transmits the exposure statespecification information to the distance measurement control unit 24,and then, the process progresses to Step 606.

In Step 606, the main control unit 26 determines whether or not endconditions which are conditions for ending this exposure statespecification information transmission processing are satisfied. Anexample of the end conditions is a condition that the power switch ofthe distance measurement device 10 is turned off. In Step 606, in a casewhere the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 600. In Step 606, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this exposure state specification informationtransmission processing ends.

Next, the light emission frequency determination processing which isexecuted by the distance measurement control unit 24 if the power switchof the distance measurement device 10 is turned on will be describedreferring to FIG. 17.

In the light emission frequency determination processing shown in FIG.17, first, in Step 610, the distance measurement control unit 24determines whether or not the exposure state specification informationtransmitted by executing the processing of Step 604 is received. In Step610, in a case where the exposure state specification informationtransmitted by executing the processing of Step 604 is not received, thedetermination is negative, and the process progresses to Step 616. InStep 610, in a case where the exposure state specification informationtransmitted by the executing the processing of Step 604 is received, thedetermination is affirmative, and the process progresses to Step 612.

In Step 612, the distance measurement control unit 24 derives the lightemission frequency corresponding to the exposure state specificationinformation received in Step 610 from the light emission frequencydetermination table 500, and then, the process progresses to Step 614.

In Step 614, the distance measurement control unit 24 stores the lightemission frequency derived in the processing of Step 612 in the storageunit 48, and then, the process progresses to Step 616. The lightemission frequency stored in the storage unit 48 by the processing ofStep 616 means “a predetermined number of times” in Step 168 of thedistance measurement processing shown in FIGS. 6 and 9.

In Step 616, the main control unit 26 determines whether or not endconditions which are conditions for ending this exposure statespecification information transmission processing are satisfied. Anexample of the end conditions is a condition that the power switch ofthe distance measurement device 10 is turned off. In Step 616, in a casewhere the end conditions are not satisfied, the determination isnegative, and the process progresses to Step 610. In Step 616, in a casewhere the end conditions are satisfied, the determination isaffirmative, and this exposure state specification informationtransmission processing ends.

In this way, since the distance measurement device 10 makes the lightemission frequency of the laser beam larger when the subject brightnessis higher, it is possible to obtain a distance measurement result, inwhich the influence of environmental noise is moderated, compared to acase where the light emission frequency of the laser beam is fixedregardless of the subject brightness.

In the foregoing embodiment and modification examples, although a casewhere the histogram relating to the measurement frequency of thedistance to the subject is generated has been illustrated, theembodiment is not limited thereto. For example, a histogram relating toa measurement frequency of the time required for reciprocation from theemission and the reception of the laser beam may be generated. A timerange corresponding to the effective distance measurement range may beset, and a histogram may be reconstructed with a resolution increasedaccording to the time range. In this case, for example, a distance tothe subject derived based on the time corresponding to the maximum valueof the reconstructed histogram may be set to distance which is finallyoutput (a distance which is provided to the user).

In the foregoing embodiment and modification examples, as shown in FIGS.4 and 18A, although an example where both end portions of the histogramby all data are not included in the effective distance measurement range(in the example shown in FIG. 18A, a non-hatched range) has beendescribed, the embodiment is not limited thereto. As an example, asshown in FIGS. 18B and 18C, one end portion (hatched portion) of thehistogram may not be included in the effective distance measurementrange (in the examples shown in FIGS. 18B and 18C, a non-hatched range).

In the foregoing embodiment and modification examples, for convenienceof description, although a case where the histogram (the histogram byall data) generated once is reconstructed based on the effectivedistance measurement range has been illustrated, the embodiment is notlimited thereto. For example, the distance measurement control unit 24may generate a histogram for the remaining distances excluding thedistances outside the effective distance measurement range among thedistances (all data) to the subject obtained by multiple times ofderivation. Even in this case, the distance measurement control unit 24may generate a histogram with the above-described derivation resolution.

In the foregoing embodiment and modification examples, although a casewhere information relating to the distance to the subject is displayedon the view finder 46 so as to be superimposed on a live view image hasbeen illustrated, the embodiment is not limited thereto. For example,information relating to the distance to the subject may be displayed ina display area different from the display area of the live view image.In this way, information relating to the distance to the subject may bedisplayed on the view finder 46 in parallel with the display of the liveview image.

In the foregoing embodiment and modification examples, although a casewhere the distance measurement imaging start button or the releasebutton provided in the distance measurement device 10 is operated hasbeen illustrated, the embodiment is not limited thereto. For example, AEand AF may be started in response to an imaging preparation instructionreceived by a user interface (UI) unit of an external device used in theform of being connected to the distance measurement device 10, andactual exposure may be started in response to an imaging instructedreceived by the UI unit of the external device. Examples of the externaldevice used in the form of being connected to the distance measurementdevice 10 include a smart device, a personal computer (PC), or aspectacles type or a wristwatch type wearable terminal device.

In the foregoing embodiment and modification examples, although a casewhere the live view image and the distance measurement result(information relating to the distance to the subject) are displayed onthe view finder 46 has been illustrated, the embodiment is not limitedthereto. For example, at least one of the live view image or thedistance measurement result may be displayed on a display unit of theexternal device used in the form of being connected to the distancemeasurement device 10. Examples of the display unit of the externaldevice used in the form of being connected to the distance measurementdevice 10 include a display of a smart device, a display of a PC, or adisplay of a wearable terminal device.

In the foregoing embodiment and modification examples, although thefocus adjustment and the exposure adjustment by AF and AE have beenillustrated, the embodiment is not limited thereto, and focus adjustmentby manual focus and exposure adjustment by manual exposure may beapplied.

In the foregoing embodiment and modification examples, although a casewhere the voltage adjustment is performed in Step 202 has beenillustrated, the embodiment is not limited thereto, and the voltageadjustment may not necessarily be performed.

In the foregoing embodiment and modification examples, in a case wherethe distance measurement control unit 24 performs the distancemeasurement, as shown in FIG. 19, the AF result (or the manual focusadjustment result) or the AE result is acquired from the main controlunit 26. Then, at least one of the laser diode 32 or the photodiode 36may be driven and adjusted based on the respective results.

The respective processing shown in the flowcharts described in theforegoing embodiment and modification examples are merely examples.Accordingly, it is needless to say that unnecessary steps may bedeleted, new steps may be added, or the processing order may berearranged without departing the gist of the invention. The respectiveprocessing included in the distance measurement processing or thedistance measurement error processing described above may be realized bya software configuration using a computer by executing a program, or maybe realized by other hardware configurations. Furthermore, therespective processing may be realized by a combination of a hardwareconfiguration and a software configuration.

In the foregoing embodiment and modification examples, although thedistance measurement device has been described as an example, thetechnique of the present disclosure may be applied to an imaging device,such as a digital camera.

In addition, the configurations, operations, and the like of thedistance measurement device 10 and the like described in the foregoingembodiment and modification examples are examples, and obviously, may bemodified depending on the situation without departing from the spirit ofthe present disclosure.

In the foregoing embodiment, although the laser beam has beenillustrated as light for distance measurement, the embodiment is notlimited thereto, and directional light which is light having directivitymay be used. For example, directional light which is obtained by a lightemitting diode (LED) or a super luminescent diode (SLD) may be used. Thedirectivity of directional light is preferably the same directivity asthe directivity of the laser beam, and is preferably, for example, thedirectivity usable in a distance measurement within a range of severalmeters to several kilometers.

All documents, patent applications, and technical specificationsdescribed in this specification are incorporated by reference in thisspecification as if each of the documents, the patent applications, andthe technical specification is concretely and respectively specified asbeing incorporated by reference herein.

In regard to the above embodiment, the following appendixes are furtherdisclosed.

APPENDIX 1

A distance measurement device comprising an imaging unit which capturesa subject image formed by an imaging optical system forming the subjectimage indicating a subject, an emission unit which emits a laser beamalong an optical axis direction of the imaging optical system, a lightreceiving unit which receives reflected light of the laser beam from thesubject, a derivation unit which derives a distance to the subject basedon the timing at which the laser beam is emitted by the emission unitand the timing at which the reflected light is received by the lightreceiving unit, a display unit which displays the subject image capturedby the imaging unit, and a control unit which performs control suchthat, in a case of performing a distance measurement by the emissionunit, the light receiving unit, and the derivation unit, the displayunit displays the subject image captured by the imaging unit as a motionimage and transition is made to a state where actual exposure by theimaging unit is possible at the timing of the end of the distancemeasurement.

APPENDIX 2

A distance measurement method comprising, in a case of performing adistance measurement to derive a distance to a subject based on thetiming at which a laser beam is emitted by an emission unit emitting thelaser beam along an optical axis direction of an imaging optical systemforming a subject image indicating a subject and the timing at whichreflected light is received by a light receiving unit receiving thereflected light of the laser beam from the subject, displaying thesubject image captured by an imaging unit capturing the subject image ona display unit as a motion image and transitioning to a state whereactual exposure by the imaging unit is possible at the timing of the endof the distance measurement.

APPENDIX 3

A distance measurement program which causes a computer to executeprocessing including, in a case of performing a distance measurement toderive a distance to a subject based on the timing at which a laser beamis emitted by an emission unit emitting the laser beam along an opticalaxis direction of an imaging optical system forming a subject imageindicating a subject and the timing at which reflected light is receivedby a light receiving unit receiving the reflected light of the laserbeam from the subject, displaying the subject image captured by animaging unit capturing the subject image on a display unit as a motionimage and transitioning to a state where actual exposure by the imagingunit is possible at the timing of the end of the distance measurement.

What is claimed is:
 1. A distance measurement device comprising: animage sensor that captures a subject image formed by an imaging opticalsystem forming the subject image indicating a subject; a display thatdisplays the subject image captured by the image sensor; and a processorconfigured to perform a distance measurement that derives a distance tothe subject, and to perform control such that, in a case of performingthe distance measurement, the display displays the subject imagecaptured by the image sensor, actual exposure by the image sensor isperformed after the timing of the end of the distance measurement, andthe display continues display of the subject image at least until thetiming of the end of the distance measurement.
 2. The distancemeasurement device according to claim 1, further comprising: an emitterthat emits directional light as light having directivity; and a lightreceiver that receives reflected light of the directional light from thesubject, wherein, the processor is configured to perform the distancemeasurement based on the timing at which the directional light isemitted by the emitter and the timing at which the reflected light isreceived by the light receiver.
 3. The distance measurement deviceaccording to claim 2, wherein the timing of the end of the distancemeasurement is the timing of the end of a period during which lightemission and light reception are performed by the emitter and the lightreceiver.
 4. The distance measurement device according to claim 1,wherein the timing of the end of the distance measurement is the timingof the end of a derivation period during which the distance is derivedby the processor.
 5. The distance measurement device according to claim1, wherein the image sensor performs the actual exposure by the imagesensor in a case where the distance is derived by the processor.
 6. Thedistance measurement device according to claim 1, further comprising: asetting unit that sets whether or not to perform the actual exposure bythe image sensor in advance in a case where the distance measurement isimpossible.
 7. The distance measurement device according to claim 1,further comprising: a memory that stores the distance derived by theprocessor, wherein, in a case where the distance measurement isimpossible, storage by the memory is stopped.
 8. The distancemeasurement device according to claim 6, further comprising: a storagesetting unit that sets whether or not to stop storage by the memory in acase where the derivation of the distance by the processor isimpossible.
 9. The distance measurement device according to claim 1, theprocessor further configured to perform focus adjustment of the imagingoptical system to the subject based on the distance derived by theprocessor.
 10. The distance measurement device according to claim 1,wherein the distance measurement is performed a number of timesdetermined in advance according to subject brightness or exposure statespecification information.
 11. The distance measurement device accordingto claim 10, wherein the distance measurement is performed a largernumber of times when the subject brightness is higher or when theexposure indicated by the exposure state specification information islower.
 12. A distance measurement method comprising: causing an imagesensor to capture a subject image formed by an imaging optical systemforming the subject image indicating a subject; displaying the capturedsubject image on a display; performing a distance measurement to derivea distance to the subject; and performing control such that actualexposure by the image sensor is performed after the timing of the end ofthe distance measurement, and that the display continues display of thesubject image at least until the timing of the end of the distancemeasurement.
 13. A non-transitory computer-readable storage mediumstoring a program that causes a computer to execute distance measurementprocessing, the distance measurement processing comprising: causing animage sensor to capture a subject image formed by an imaging opticalsystem forming the subject image indicating a subject; displaying thecaptured subject image on a display; performing a distance measurementto derive a distance to the subject; and performing control such thatactual exposure by the image sensor is performed after the timing of theend of the distance measurement, and that the display continues displayof the subject image at least until the timing of the end of thedistance measurement.
 14. The distance measurement device according toclaim 2, wherein driving of the light receiver is adjusted according toinformation of an exposure adjustment.
 15. The distance measurementdevice according to claim 2, wherein, when a second focal distance isshorter than a first focal distance, an emission intensity of theemitter for the second focal distance is set lower than an emissionintensity of the emitter for the first focal distance.
 16. The distancemeasurement device according to claim 2, wherein, when a second focaldistance is shorter than a first focal distance, a receiving sensitivityof the light receiver for the second focal distance is set lower than areceiving sensitivity of the light receiver for the first focaldistance.
 17. The distance measurement device according to claim 2,wherein, when a second exposure state is higher in exposure than a firstexposure state, an emission intensity of the emitter for the secondexposure state is set lower than an emission intensity of the emitterfor the first exposure state.
 18. The distance measurement deviceaccording to claim 1, wherein the display displays information relatingto the distance to the subject.
 19. The distance measurement deviceaccording to claim 1, wherein the processor is configured to, when poweris supplied to the distance measurement device, control the display tostart displaying the subject image captured by the image sensor, andcontrol the display to continue displaying the subject image until powersupply is turned off.
 20. A digital camera comprising: the distancemeasurement device according to claim 1.